Polymers and copolymers may be formed from olefinic monomers by using transition metal metallocene catalyst technology. This well-known technology uses catalysts containing early transition metal atoms such as Ti and Zr.
Even though polyolefins formed by such metallocene catalysts posses enhanced properties over polyolefins produced by conventional Ziegler-Natta catalysts, further improvements in properties such as wettability and adhesiveness may be possible. It is believed that including polar monomers in an olefinic polymer or copolymer would improve wettability and adhesiveness in those materials. Unfortunately, polar monomers tend to poison early transition metal catalysts.
Certain late transition metal complexes of palladium and nickel incorporate some polar monomers. However, such catalyst systems are costly. Also, the polymers so produced are highly branched (85-150 branches/1000 carbon atoms) and the functionalities are not in the chain but at the ends of branches. Consequently, they are limited to polar monomer contents.ltoreq.about 15 mol %. Another disadvantage of these systems is that they incorporate only a limited number of polar monomers (e.g. alkyl acrylates and vinyl ketones). Methyl methacrylate and n-butyl vinyl ether are mildly inhibiting or inert.
Consequently, there remains a need for a polymerization catalyst capable of forming olefinic polymers and copolymers and that are effective polymerization catalysts in the presence of polar monomers.